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91.
Two leucine aminopeptidase M inhibitors, cyanostatin A and B, were isolated from cyanobacterial water blooms at Loch Rescobie in Scotland, and specifically from a Microcystis species. Both inhibitors were lipopeptides containing 3-amino-2-hydroxydecanoic acid and weak inhibitors of protein phosphatase (PP2A). Both strongly inhibited the activity of leucine aminopeptidase M with IC50 values of 40 and 12 ng/ml, respectively. 相似文献
92.
Maria do Carmo Bittencourt-Oliveira Mariana Cabral de Oliveira Christopher J. S. Bolch 《Journal of phycology》2001,37(5):810-818
The genetic and morphological variability among 15 Brazilian strains of Microcystis aeruginosa (Kütz.) Kütz. collected from four locations was examined and compared with several reference strains of M. aeruginosa , M. viridis (A. Br.) Lemm. and M. wesenbergii (Kom.) Kom. in Kondr. Brazilian strains were classified by morphological features and by comparison of the nucleotide sequences of the cpc BA intergenic spacer and flanking regions. Our results indicate that Brazilian strains classified as M. aeruginosa are phylogenetically diverse compared with reference strains of M. aeruginosa and that the current taxonomy underestimates genetic diversity within M. aeruginosa. The data also demonstrate that morphological criteria alone are inadequate to characterize Microcystis species. Although colonial characters were shown to vary considerably in culture, some genetic lineages demonstrated consistent cellular diameter ranges, indicating that cell size has value as a taxonomic character. The detection of six M. aeruginosa genotypes in a single water body indicates that morphological approaches can also seriously underestimate the diversity of Microcystis bloom populations. 相似文献
93.
94.
《African Journal of Aquatic Science》2013,38(3):313-321
Blooming and non-blooming periods between 2004 and 2006 in a hypereutrophic reservoir, where cyanobacterial blooms have previously been reported to be permanent, presented an opportunity to characterise factors that may favour cyanobacterial dominance. As a bloom developed in May 2004, a shift to dominance by Microcystis aeruginosa, similar to competitive exclusion, was observed. The period of M. aeruginosa dominance was characterised by the lowest Secchi depth and euphotic zone depth readings, and a decline of non-buoyant species because of competitive exclusion by M. aeruginosa, which reduced light availability in the water column. After the bloom collapsed, the euphotic zone depth increased, followed by the establishment of a Cryptomonas–Cyclotella phytoplankton assemblage. Cyanobacterial dominance within the phytoplankton assemblage was favoured by an extended stratification and was limited by nitrogen (mainly ammonium) availability. Other taxa were limited by light availability, as shown by their decline when M. aeruginosa dominated. The period of extended stratification, an increase in ammonium concentration and a decrease in nitrate concentration promoted dominance by M. aeruginosa. 相似文献
95.
Micheline Kézia Cordeiro‐Araújo Maria do Carmo Bittencourt‐Oliveira 《Phycological Research》2013,61(1):1-6
The active release of microcystins in cyanobacterium Microcystis aeruginosa (Kützing) Kützing, strain BCCUSP232 was confirmed. The microcystin release is controlled by an endogenous rhythm, pointing to a biosynthetic pattern of toxins in cyanobacteria. Proofing tests for this active release were carried out by experiments at two independent 24 h cycles, light : dark and continuous light (12:12 h) along the exponential growing phase. Cultivation samples at light, temperature and photoperiod controlled conditions were collected in 2‐h intervals. Microcystin concentrations from the pellet aliquots (intracellular microcystin per cell‐quota –IMC) and supernatant (extracellular microcystin per equivalent cell‐quota – EMC) were quantified with enzyme linked immunosorbent assay. The IMC concentrations showed increases and decreases in both cycles. Decreases of IMC clearly demonstrate that the toxin was actively released to the surrounding medium and not by cell lysis. The total microcystins concentrations (IMC and EMC) between the light : dark and continuous light cycles presented similar variations between the same hours. 相似文献
96.
ABSTRACT We evaluated the ultrastructural variations occurring during a surface bloom in Microcystis aeruginosa Kützing PCC 7005, by comparing cultures exposed to high incident light irradiance (90 µmol photons m-2 s-1) and to low irradiance (9 µmol photons m-2 s-1). At 12h, and 15 and 30 days in culture, the cells were fixed in glutaraldehyde and subjected to cytochemical assays. Exposure to high irradiance induced structural changes in the cell wall, and differences in the photosynthetic apparatus and granule reserves. After 15 days of high irradiance, the following features were observed: a reduced number of thylakoids and changes in their arrangement; high accumulation of glycogen, poly-beta-hydroxybutyrate, lipid bodies and cyanophycin; conspicuous structural changes in the cell wall. At day 30 of high irradiance, the viable cells had few thylakoids, arranged parallel to each other and perpendicular to the plasma membrane, and abundant glycogen. Nitrogen, calcium and phosphorus, as detected by electron spectroscopic imaging, were present in different sites of cells grown at low and high irradiance. The results of this study, together with previous data on variation in Fe-superoxide dismutase (Canini et al., 2001a), suggest that defense mechanisms against high and prolonged irradiance only operate for a short time. 相似文献
97.
98.
Dedmer B Van de Waal Jolanda MH Verspagen Jan F Finke Vasiliki Vournazou Anne K Immers W Edwin A Kardinaal Linda Tonk Sven Becker Ellen Van Donk Petra M Visser Jef Huisman 《The ISME journal》2011,5(9):1438-1450
Climate change scenarios predict a doubling of the atmospheric CO2 concentration by the end of this century. Yet, how rising CO2 will affect the species composition of aquatic microbial communities is still largely an open question. In this study, we develop a resource competition model to investigate competition for dissolved inorganic carbon in dense algal blooms. The model predicts how dynamic changes in carbon chemistry, pH and light conditions during bloom development feed back on competing phytoplankton species. We test the model predictions in chemostat experiments with monocultures and mixtures of a toxic and non-toxic strain of the freshwater cyanobacterium Microcystis aeruginosa. The toxic strain was able to reduce dissolved CO2 to lower concentrations than the non-toxic strain, and became dominant in competition at low CO2 levels. Conversely, the non-toxic strain could grow at lower light levels, and became dominant in competition at high CO2 levels but low light availability. The model captured the observed reversal in competitive dominance, and was quantitatively in good agreement with the results of the competition experiments. To assess whether microcystins might have a role in this reversal of competitive dominance, we performed further competition experiments with the wild-type strain M. aeruginosa PCC 7806 and its mcyB mutant impaired in microcystin production. The microcystin-producing wild type had a strong selective advantage at low CO2 levels but not at high CO2 levels. Our results thus demonstrate both in theory and experiment that rising CO2 levels can alter the community composition and toxicity of harmful algal blooms. 相似文献
99.
100.
Sato Y Morimoto K Hirayama M Hori K 《Biochemical and biophysical research communications》2011,(2):291-296
The carbohydrate binding profile of the red algal lectin KAA-2 from Kappaphycus alvarezii was evaluated by a centrifugal ultrafiltration–HPLC method using pyridylaminated oligosaccharides. KAA-2 bound exclusively to high mannose type N-glycans, but not to other glycans such as complex type, hybrid type, or the pentasaccharide core of N-glycans. This lectin exhibited a preference for an exposed α1–3 Man on a D2 arm in a similar manner to Eucheuma serra agglutinin (ESA-2), which shows various biological activities, such as anti-HIV and anti-carcinogenic activity. We tested the anti-influenza virus activity of KAA-2 against various strains including the recent pandemic H1N1-2009 influenza virus. KAA-2 inhibited infection of various influenza strains with EC50s of low nanomolar levels. Immunofluorescence microscopy using an anti-influenza antibody demonstrated that the antiviral activity of KAA-2 was exerted by interference with virus entry into host cells. This mechanism was further confirmed by the evidence of direct binding of KAA-2 to a viral envelope protein, hemagglutinin (HA), using an ELISA assay. These results indicate that this lectin would be useful as a novel antiviral reagent for the prevention of infection. 相似文献